I. Field of the Invention
This invention relates generally to a motorized vehicle for pulling shopping carts, and more particularly to a cart pulling vehicle with dual cable drums and dual torsion springs.
II. Discussion of the Prior Art
In the past, collection of shopping carts from parking lots was done by manual pushing of a string of carts by a store employee. As these carts were retrieved, the line of carts being pushed would grow longer and more difficult to maintain control. Two workers were required, one at the rear of the string to push and one at the front to steer. Therefore, the number of carts that were retrieved at one time was comparatively limited. Not only was this manual process time-consuming and manpower intensive, it was also a strenuous activity requiring physical strength and agility.
In response to the difficulty experienced in retrieving shopping carts, several motorized devices began to be utilized. One such device is disclosed in U.S. Pat. No. 6,220,379. This device is basically a small electrically powered cart which can be either driven or operated by remote control. The device uses a pushing from the rear technique.
Another, more closely related, prior art design uses a rope extending from a motorized vehicle to the last cart in a line to pull the carts in a train-like fashion. These prior pulling machines generally have two rope play-out and take-up drums on a common shaft and a single torsion reaction spring with a single lock mechanism. The lock mechanism is controlled by switch when the handle is placed in working position. A rope extends from one drum out the rear of the machine to a rope pull and is returned to the drum on the other side of the machine. This device allows the rope to  be free to extend or retract when the lock is engaged. Unfortunately, this design has a substantial number of problems. Because the single torsion spring is attached to both drums, tension is only provided to the side with the tightest length of rope. Often the other length of rope does not have enough tension to keep it from dragging on the ground, especially when rounding corners. While this problem is intended to be addressed with the pulleys, they prove to be only marginally effective due to friction and rotational resistance. The lack of tension on one side often causes the rope on that side to unspool from its drum. Torsion spring life also is a problem due to limited space on the machine, the fact that the spring is on a common shaft with the drums, and the large number of extend/retract cycles to which the machine and spring are subjected. Finally, the rope used is also a problem because the rope is heavy and bulky to withstand the load exerted by the carts and is vulnerable to the negative effects of rubbing.
Therefore, what is needed is the cart pulling vehicle of the present invention which effectively eliminates the requirements of physical strength and agility without the tension, torsion spring life, and rope problems of the past.